Lithium Predoping Silicon Electrodes Volume Expansion
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Solution Overview
Problem
Silicon-base materials for lithium ion batteries exhibit high capacity but low first cycle charge/discharge efficiency and significant volume change during lithium doping and dedoping, leading to capacity decline in cycle operation.
Innovation Solution
A method involving kneading and mixing lithium metal with silicon-base materials, such as silicon and silicon dioxide, in the presence of a specific solvent to predope the materials, which are then coated with carbon and used in electric storage devices with a binder to suppress volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-base material is used as negative electrode to increase capacity, then energy density is improved, but first cycle charge/discharge efficiency deteriorates and volume change increases
Solution Approach 1:
The patent applies preliminary action by predoping the silicon-base material with lithium ions before the material is incorporated into the battery electrode. This pre-introduction of lithium ions into the silicon structure prevents the severe volume expansion that occurs during first-cycle charging, thereby improving first cycle charge/discharge efficiency while maintaining the high capacity benefit of silicon-based materials
2Quantity of substance
If silicon-base material is used as negative electrode to increase capacity, then energy density is improved, but volume change during cycling increases
Solution Approach 1:
The patent applies preliminary action by predoping the silicon-base material with lithium ions before the material is incorporated into the battery electrode. This pre-introduction of lithium ions into the silicon structure prevents the severe volume expansion that occurs during first-cycle charging, thereby improving first cycle charge/discharge efficiency while maintaining the high capacity benefit of silicon-based materials
3Quantity of substance
If conventional predoping method with lithium metal foil is used, then lithium predoping is achieved, but process complexity increases and handling difficulty arises
Solution Approach 1:
The patent replaces the mechanical handling of lithium metal foil with a chemical solution-based approach. Instead of manually attaching and handling thin lithium metal foils, the invention uses a lithium-containing solution that can be uniformly applied to the electrode substrate, eliminating the mechanical complexity and handling difficulties associated with conventional methods
Solution Approach 2:
The patent introduces a lithium-containing solution as an intermediary medium to transfer lithium ions to the electrode. This solution acts as a mediator between the lithium source and the electrode material, enabling uniform predoping without the need for direct contact with lithium metal foil, thereby simplifying the overall process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables uniform and efficient lithium predoping, improving the first cycle charge/discharge efficiency and reducing volume changes, thus enhancing the performance and stability of silicon-base material electrodes in lithium ion batteries.
Implementation Method 1
kneading and mixing lithium metal with silicon-base materials... to predope the materials
Implementation Method 2
which are then coated with carbon
Data Source
AI summary
A predoping method for lithium, which is characterized by mixing and kneading, in the presence of a solvent, lithium metal with (a) silicon and a composite dispersion of silicon and silicon dioxide, (b) particles represented by SiOx (wherein 0.5≦x<1.6) and having a fine structure wherein fine silicon particles are dispersed in a silicon-based compound, and (c) an Si-based material that is a mixture of one or more oxides selected from among the lower oxides of silicon represented by the above-mentioned formula and that is capable of absorbing and desorbing lithium ions; a lithium-predoped electrode which uses the predoping method for lithium; and an electricity storage device.